import math

def main():
    x1, y1, x2, y2 = [float(n) for n in input().split()]

    d = math.sqrt((x2 - x1)**2 + (y2 - y1)**2)

    print("{:.5f}".format(d));

if __name__ == '__main__':
    main() import math math def main():
    x1, y1, x2, y2 = [float(n) for n in input().split()]

    d = math.sqrt((x2 - x1)**2 + (y2 - y1)**2)

    print("{:.5f}".format(d)); main float(n) for n in input().split() for n in input().split() n input().split() ().split () input split for n in input().split() float(n) float n x1, y1, x2, y2 = [float(n) for n in input().split()] x1 [float(n) for n in input().split()] y1 x2 y2 d = math.sqrt((x2 - x1)**2 + (y2 - y1)**2) d math.sqrt((x2 - x1)**2 + (y2 - y1)**2) math.sqrt math sqrt (x2 - x1)**2 + (y2 - y1)**2 (x2 - x1)**2 x2 - x1 x2 x1 2 (y2 - y1)**2 y2 - y1 y2 y1 2 print("{:.5f}".format(d)) print "{:.5f}".format(d) "{:.5f}".format "{:.5f}" format d if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    x1, y1, x2, y2 = [float(n) for n in input().split()]

    d = math.sqrt((x2 - x1)**2 + (y2 - y1)**2)

    print("{:.5f}".format(d)); def main():
    x1, y1, x2, y2 = [float(n) for n in input().split()]

    d = math.sqrt((x2 - x1)**2 + (y2 - y1)**2)

    print("{:.5f}".format(d)); main
import math

def main():
    x1, y1, x2, y2 = [float(n) for n in input().split()]

    d = math.sqrt((x2 - x1)**2 + (y2 - y1)**2)

    print("{:.5f}".format(d));

if __name__ == '__main__':
    main()
